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post #8 of Old 11-13-2012
Maine Sail
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Re: Bilge pump non return valve.

Originally Posted by Hartley18 View Post
Maine, there are instances where you might need to install a check valve (I needed to) and ways to do so that doesn't give rise to the "standing water in the discharge hose" you mention (install it high up near the discharge point - not in the bilge with the pump itself).. I guess exactly what you do depends on the specific circumstances and the type of boat.

I've known check valves to fail open (bits of rubbish preventing the flap closing), but I've never heard of one sticking closed.. but then we don't get the freezing weather you get. I've known of boats that sank because there was no check valve fitted when they needed one..

IMHO, the bottom line is: Don't install a check valve unless your particular installation means you have no other alternative.

BTW, the other thing that can prevent the pump pumping is lack of a strum box.. make sure you use one.
If you want to use a two pump system a "nuisance pump" and a "primary" pump then a check valve can be fitted to the lower nuisance water pump. they still stick and kill batteries though... I would NEVER, and I don't use the word never often, recommend a check valve on a single pump installation when a centrifugal pump is being used. If you want a check valve please use a rotary vane or diaphragm pump that has the ability to deal with the head pressure of the standing water and to push open a sticky check valve... Centrifugal pumps often just make neat little bubbles and the water remains in the bilge.

It is your boat, you can do as you wish, but check valves on centrifugal pumps are a danger waiting to happen. You would be horrified at the number of "check valves" I see that fail to open. I am the guy replacing the batteries that the bilge pump killed when the check valve stuck and the float switch remained ON.........

-Maine Sail / CS-36T

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